USB HDMI Capture

Rice · March 22, 2025, 3:52pm

Mabey it’s a Linux limitation thing then. I accidentally plugged it into a usb2.0 on the back of my motherboard and I got 9fps max. It wouldn’t work in channels until it was back on 3.0. Ymmv

Howesey2k · March 23, 2025, 1:29pm

@tmm1 Any joy in stopping it from spinning after a successful stream? I thought maybe make the script disconnect from the HDMI dongle when a stream closes. Like a software version of pulling the usb out and back in

Rice · March 24, 2025, 4:33pm

@tmm1
Is there anything you can do about these errors in the logs? I have hundreds of thousands of these lines when the capture is active making it impossible to find anything in the logs. 100-150 of these lines a second.


2025/03/24 11:27:50.801386 [HLS] ffmpeg: capture-usb-hdmi:  PTS 1252804028406, next:533312 invalid dropping st:0
2025/03/24 11:27:50.802936 [HLS] ffmpeg: capture-usb-hdmi:  DTS 1252804045070, next:549978 st:0 invalid dropping
2025/03/24 11:27:50.802975 [HLS] ffmpeg: capture-usb-hdmi:  PTS 1252804045070, next:549978 invalid dropping st:0
2025/03/24 11:27:50.815313 [HLS] ffmpeg: capture-usb-hdmi:  DTS 1252804061741, next:566644 st:0 invalid dropping
2025/03/24 11:27:50.815373 [HLS] ffmpeg: capture-usb-hdmi:  PTS 1252804061741, next:566644 invalid dropping st:0
2025/03/24 11:27:50.836848 [HLS] ffmpeg: capture-usb-hdmi:  DTS 1252804078397, next:583310 st:0 invalid dropping
2025/03/24 11:27:50.836856 [HLS] ffmpeg: capture-usb-hdmi:  PTS 1252804078397, next:583310 invalid dropping st:0
2025/03/24 11:27:50.858475 [HLS] ffmpeg: capture-usb-hdmi:  DTS 1252804095061, next:599976 st:0 invalid dropping
2025/03/24 11:27:50.858509 [HLS] ffmpeg: capture-usb-hdmi:  PTS 1252804095061, next:599976 invalid dropping st:0
2025/03/24 11:27:50.880197 [HLS] ffmpeg: capture-usb-hdmi:  DTS 1252804111730, next:616642 st:0 invalid dropping
2025/03/24 11:27:50.880230 [HLS] ffmpeg: capture-usb-hdmi:  PTS 1252804111730, next:616642 invalid dropping st:0

Rice · March 24, 2025, 5:19pm

Thank you!!

Howesey2k · March 25, 2025, 5:51pm

Thank you again for getting this to work on Linux. The only issue I am facing now is an audio video syncing issue. Is there anything that can be done to improve it? It's not horrendous but noticeable Thank you again for your hard work.

Howesey2k · March 28, 2025, 10:12pm

Hi @tmm1 I found this about ffmpeg. Might this help my syncing issues?

Correct FFmpeg Sync Audio to Video That is Too Fast or Slow
You can easily do this by using the -async parameter of FFmpeg, which, as per the documentation "Stretches/squeezes" enables the sound stream to match the timestamps. The parameter takes a numeric value for the samples per second to fix the issue.

ffmpeg -async 25 -i input.mpg -r 25

Attempt gradually expanding the - async value until the sound and video are in sync.

Many thanks

hancox · March 30, 2025, 10:29am

turtletank:

MacOS 15.3.1

So MacOS considers these devices to be cameras and applies strict Privacy & Security restrictions to them.

I did some research this morning and as far as I can tell it is just not possible to access a camera from a process that is running as a LaunchAgent. It seems this was an intentional decision made by Apple and to be fair it makes sense.

With a standard installation of Channels DVR, ffmpeg will just hang as it never receives any video input.

For testing purposes I was able to work around this by running Channels DVR manually.
launchctl unload ~/Library/LaunchAgents/com.getchannels.dvr.plist
cd ~/Library/Application\ Support/ChannelsDVR/data
../latest/channels-dvr
and the following to run Channels normally when you are finished
launchctl load ~/Library/LaunchAgents/com.getchannels.dvr.plist
@tmm1 have you found a good workaround for this?

Still scratching my head at this - @tmm1 are you running your mac DVR manually? It's just so odd that yours worked straight away on post 1, and everyone else has the same issue as the quoted post.